Pre-treatment of wood chips before pulp digester cooking processes

摘要

Wood chips(1) are steamed at atmospheric pressure in a gas phase part of the low-pressure system followed by a liquid phase in chip chute(3). A high-pressure feeder(4) takes the pre-treated wood chips for feeding to a digester vessel(19). Low-pressure liquid(5) is pumped(6) through a sand trap(7) and in-line strainer(8) back into the chip chute(3). A level tank(9) controls liquid levels in the chute(3). Hot process liquids(11,12) from the high pressure cooking system are flashed in the level tank(9) to provide heating steam for the low-pressure system. The cooled liquid is used as make-up for the circulation liquid in the low-pressure system.